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I think it's being able to handle gracefully this one:

a * -2 + b * 5 = -9

Yields me several interpretations, one of them I like:

a = 5n + 2, b = 2n - 1, n ∊ ℤ

Now because a and b are Stack Exchange downvotes and upvotes on questions; and if I fed a 0 to the solution it handed me, it would yield a = 2, b = -1 where b fails to be in ℕ; I tried to apply an additional constraint to it:

a * -2 + b * 5 = -9 such that a > -1 and b > -1

But I'm unable to find such interpretation in the answers it's proposing me.

How to / What am I doing wrong?

85579
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  • You can examine your solution and determine that $n\ge 1$ will force both constraints to be satisfied. – Adrian Keister Sep 17 '19 at 18:32
  • But then I would want to enter a * -2 + b * 5 = -9 such that n > 0 instead of a * -2 + b * 5 = -9 such that a > -1 and b > -1 and my material issue with using the tool prevails. – 85579 Sep 17 '19 at 18:36
  • In Mathematica (which is generally superior to W|A in these situations), you can probably use the Assumptions->{a>-1, b>-1} command. That might even work in W|A, but it's not guaranteed. But my point above is that you don't actually need that in this case. – Adrian Keister Sep 17 '19 at 18:43

1 Answers1

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I think 

a * -2 + b * 5 = -9, a > -1, b > -1

did what I wanted. At first I thought it was interpreting a tuple, but I finally found

a = 5n + 2, b = 2n - 1, n ∊ ℤ, n ≥ 1

as the last interpretation.

85579
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